Field of the Invention
The invention relates to a sheet feed for printing presses, in particular offset presses, having a pile table for receiving a pile of sheets thereon, the pile table being located between feed side elements and being vertically movable by means of a main pile lifter, and having an auxiliary pile lift for uninterrupted or so-called non-stop sheet delivery when a new pile of sheets is placed therein, the auxiliary sheet lift having non-stop rails for coordinating non-stop rods or the like supporting a residual sheet pile.
Sheet feeds in printing presses serve to separate sheets from a pile of sheets and deliver them to the printing mechanism of the printing press. Because the height of the sheet pile decreases as the withdrawal of sheets progresses, the pile is located on a vertically movable pile table, so that as the pile height decreases, the pile table can be moved correspondingly upwardly, so that the topmost sheets remain within an operative range of a suction head arrangement which takes the sheets from the pile and delivers them to the sheet transport path of the printing press. To assure uninterrupted sheet delivery, a so-called auxiliary pile lift is provided, which receives the residual sheet pile left over from a pile of sheets during the delivery of a new sheet pile. The new sheet pile is placed beneath the residual sheet pile, and the residual sheet pile and the new sheet pile are then combined.
Sheet feeds in printing presses are known in which the pile table which receives the main pile is suspended from support chains which are driven via sprocket wheels. The suspension of the support chains is effected via deflector sprocket wheels, which are supported on a crossbar disposed above the sheet pile. Because of the crossbar, the structure is very high, and the view of the paper stream is obstructed.
So-called compact feeds are therefore also known, in which the structure is somewhat lower, because a crossbar is not required. Instead, feed side walls facing one another at a spaced distance are provided, between which the sheet pile is deposited on a pile table. The pile table rests on vertical guides which are disposed on inner sides of the feed side walls. At the same time, above the pile table, these vertical guides receive lift slide blocks of an auxiliary pile lift; that is, the main pile lift and the auxiliary pile lift both use the same vertical guides. As a result, however, the vertical guides must be relatively long and hence must extend to a corresponding height, because even if the pile table lift slide block is moved far upwardly, there must still be an available region of the guide above this lift slide block in order to receive the lift slide blocks of the auxiliary pile lift. Moreover, it is necessary for the non-stop rails secured to the lift slide blocks of the auxiliary pile lift to be bent downwardly at a right angle, so that non-stop rods to be placed thereon will stay at the correct working height for the residual sheet pile. However, the fact that the guides protrude relatively far upwardly leads to the same disadvantages that exist in sheet feeds with crossbars; that is, both the accessibility and the view are hindered; for an operator standing on an operator platform installed to the side of the feed side wall located on the side of the operator, the view of the paper stream is obstructed. Moreover, the high structural form causes problems in terms of achieving accident prevention.